turbofan

/ˈtɜːbəʊˌfæn/

noun

1.

Also called high bypass ratio engine. a type of by-pass engine in which a large fan driven by a turbine and housed in a short duct forces air rearwards around the exhaust gases in order to increase the propulsive thrust

(tûr'bō-fěn') A type of gas turbine in which the fan driving air into a turbojet also forces additional air around the outside of the turbine, combining it with the exhaust of the turbojet to provide thrust. Turbofans are quieter than simple turbojets and somewhat more fuel efficient, and are widely used in commercial aircraft.